Technical Abstract: Buried seed in pasture soils are often reservoirs of weedy plants. The seed bank was characterized in pastures and hayfields with different management histories at the University of New Hampshire Organic Research Dairy. Three hayfields [two of alfalfa (Medicago sativa L.) and one grass] and five pastures were sampled in August 2007. At each site, two soil cores (1.88 cm diameter by 5 cm deep) were taken at 27 georeferenced points within a 20- by 50-m modified Whitaker plot. Soil samples were placed in a greenhouse for 5 months and germinated seedlings counted regularly. Soil from the hay fields had the fewest number of seed (8 to 83 seeds per plot sample) and plant species (2 to 14 per plot sample) compared with pastures. Pastures had 98 to 277 seeds per plot sample and 12 to 25 plant species. Nearly 42% of the soil samples from the hay fields had no germinable seeds, whereas only 7% of soil samples from pastures had no germinable seeds. Grasses (Agrostis spp. and Festuca rubra L.) were most abundant in the pastures and grass hayfield. Ragweed (Ambrosia artemisifolia L.) and slender rush (Juncus tenuis L.) predominated in the seed bank from the alfalfa fields.